1. Field of the Invention
This invention relates to a method of producing a wafer such as a semiconductor wafer of silicon monocrystal and a wafer material of quartz.
2. Prior Art
In the manufacture of a wafer of a semiconductor material such as silicon and gallium arsenic as well as a thin substrate or wafer material of quartz, sapphire or the like, a rod-like stock is successively cut into slices to produce the wafers. Generally, the rod-like stock is cut by a cutter of the type having a thin cutter blade of an annular shape having an inner peripheral cutting edge. More specifically, the rod-like stock is introduced into the annular cutter blade in a direction perpendicular to the annular cutter blade, and then the rod-like stock is transversely moved relative to the annular cutter blade which rotates at a high speed about an axis thereof, so that the rod-like stock is brought into cutting engagement with the inner peripheral cutting edge and is cut to produce a slice serving as a wafer.
The wafer thus cut from the rod-like stock is slightly warped due to the inherent accuracy of the above-mentioned cutter, a variation in accuracy of attachment of the annular cutter blade and a variation in balance of cutting resistances offered respectively by opposite inner marginal portions of the annular cutter blade around the inner peripheral cutting edge. And, it has been desired to eliminate such warp. The degree of warp depends on the material of which the wafer is made and the thickness and diameter of the wafer, and generally such warp is on the order of several .mu.m to several tens of .mu.m. The warped wafer sliced from the rod-like stock has curved opposite side faces. Even if it is desired to process one of the opposite side faces of the warped wafer into a flat surface, using the other side face as a reference surface, this can not be done since the opposite side faces are curved. And, the warp can not be removed from the sliced wafer by lapping, etching and polishing. Therefore, the warp of the wafer, which develops when the wafer is cut from the rod-like stock by the annular cutter blade, adversely affects the dimensional accuracy of the final product. This problem is serious particularly where the semiconductor wafer has a relatively large diameter with a highly-densed circuitry fabricated thereon to provide an integrated circuit. Thus, the warp of the wafer presents an obstacle to a highly dense integrated circuit.